1. Field of the Invention
The present invention relates to a device for controlling the trajectory of a well drilled in the ground.
2. Description of the Prior Art
There are many well-known systems allowing control of the well inclination, for example by using a remote-controlled variable-diameter stabilizer. For azimuth correction, a downhole motor included in the drill string and coupled with a bent sub, whose direction correction action is done according to the spatial orientation in the plane of the bent sub, has been used in the trade for a long time. It is clear that, with this technique, the part of the string situated above the motor must be motionless in the borehole. This correction mode is referred to as &lt;sliding&gt; mode insofar as drilling progresses by &lt;sliding&gt;. This mode has many drawbacks, notably the fact that all of the drill string is not driven in rotation.
Directional drilling means that can work in a rotary mode have therefore been developed. Among the tools proposed, some exert a permanent or periodic controlled lateral stress on the wall of the well, in an opposite direction to the desired one, others exert an oriented flexion on the part of the pipes situated immediately above the tool, while allowing them to rotate. In any case, the necessity of maintaining the pipes rotating combined with that of controlling a fixed spatial orientation leads to sophisticated and expensive mechanical, hydraulic and electronic options.